1. Field of the Invention
The present invention relates to an air intake system for mobile engines, especially an air intake system for automotive engines, and in particular to an air intake system that has a selectively permeable membrane to effect oxygen enrichment or oxygen depletion of the air entering into the intake.
2. Description of the Prior Art
Methods for the enrichment of and/or separation of gaseous admixtures, including gaseous admixtures of oxygen and nitrogen e.g. air, are known. In particular, a membrane formed from a polymer of a perfluorodioxole is described in PCT patent application No. W090/15662 of S.M. Nemser and I.D. Roman, published Dec. 27, 1990. These applications describe a selectively permeable membrane, for the separation of a wide variety of gaseous admixtures, formed from an amorphous polymer of perfluoro-2,2-dimethyl-1,3- dioxole. The membrane may be a supported membrane, in the form of a film or a coating on a porous support or in the form of a hollow fibre. The membrane may be used for the separation of gaseous admixtures of organic compounds e.g. gaseous fluorocarbons or volatile organic compounds, from other gases. In addition, the membranes may be used for the separation of a wide variety of gaseous mixtures, including oxygen from nitrogen i.e. to enrich air in the amount of oxygen contained therein.
The use of membrane oxygen enrichment in natural gas combustion is described by S. G. Kimura and W. R. Browall in Journal of Membrane Science, 29(1986)69-77. The article states that combustion with oxygen enriched air can substantially reduce fuel consumption in certain applications and the use of a membrane is a potentially attractive approach for producing oxygen enriched air. A silicone based oxygen enrichment membrane was fabricated and tested, giving a reduction in natural gas consumption.
Apparatus for increasing or decreasing the oxygen fraction of air to be conveyed to a consumer is disclosed by F. Wolff in published European patent application 0 024 718, published Mar. 11, 1990. Apparatus for purifying the air contained in a confined space e.g. the passenger cabin of an automobile, is disclosed in published UK patent application 2 122 103 of M. Yamamoto et al, published Jan. 11, 1984.